Multistage pump



Aug. 17, 1954 v A. HoscHLE ET AL MULTISTAGE PUMP Filed Jan. 18, 1951 e EH/Mr wif/m Maw. G A F@ M 0/ Patented Aug. 17, 1954 MULTISTAGE PUMP Adolf Hoschle and Fritz Dietrich, Stuttgart, Germany Application January 18, 1951, Serial No. 206,562

Claims priority, application Germany November 24, 1950 (Cl. S- 44) 12 Claims. l

It is generally known to use in lifting installations as operating medium especially compressed air beside other forms of energy since same can be generated and stored with comparative ease for stationary as well as portable installations. The compressed air may also simultaneously be used for different other purposes.

The pressures, however, at which the operation may be carried out usually can not be increased beyond a certain value in view of the stresses otherwise developing in all parts of the installation, such as conduits, valves, reservoir and outlet elements, and moreover in view of the extensive and dilcult measures to be taken for sealing, particularly in movable elements, which measures must be taken toassure safety of operation.

ln the pressures normally applicable for raising heavy loads the disadvantageous necessity arises of providing correspondingly high press dimensions and piston cross sections. This necessity becomes a reality if, as in portable installations, for structural reasons the storage volume of the compressed air is limited and telescopically related pressure pistons must be employed. While here the pistons successively operable need higher pressures corresponding to their decreasing crosssections, the pressure available from the storage reservoir diminishes corresponding to the adiabatic or polytropio pressure drop occurring in the use of pressure. Thus two directly opposite requirements exist which cannot be complied with, and as a result, as practice has demonstrated, stored compressed air as a direct source of energy for driving such lifting installations, especially those with telescopic pistons, is an unsuited medium.

Lifting installations operated directly with compressed air, therefore, can operate only with single lifting piston, however here, particularly with portable installations, e. g. in tilting devices, structural limits as to piston diameter and piston stroke exist. rihe power excess conditioned by the pressure drop causes harmful inertia forces by high acceleration of the load to be lifted which in the long run lead to damaging the lifting installation and its base, e. g., the portable frame.

Auxiliary installations with compressed air in which hydraulic pressure means, e. g. oil, is interposed, can remove the above mentioned defects if they comply with the requirements of a telescopic piston. Oil pumps operated by compressed air can rationally operate only with a single hydraulic piston, have limited possibilities of use and are little suited if the stroke duration is intended to be short. In order to afford relief in this case, for lifting installations pressure changers were constructed which afford a proper outward stroke of the telescopic piston after due consideration of its pressure requirements.

Such a pressure changer operates e. g. with two hydraulic pressure generators which are driven by a double-acting compressed-air piston. Thereby two hydraulic pressure steps, one for the initial stage and the other for the final stage of the lifting operation, may be generated. This pressure changer shows already a superiority over other systems by a uniformity of the extension of the telescopic piston press, by the short duration of the stroke, but in its stroke power is also bound Within certain limitations.

The present invention relates to a pneumatichydraulic multistage pressure generator or pump, especially for lifting installations with pluralstep presses in which a double-acting pneumatic drive piston directly cooperates with several hydraulic pressure generators so that the effective cross-sections of the pressure generator pistons can be selectively connected singly or in any combination.

rlf'he drawing shows an execution example of the invention subject in lengthwise section.

In a housing l a pressure-propelled piston 2 displaceable in both directions is rigidly conneoted with a pressure-generating piston 3 constituting the piston rod. As a result, piston S is displaced corresponding to the displacement of piston 2 in a housing l which is connected to housing l. In housing l is also arranged a stationary piston ll and simultaneously constitutes an inner guide for the piston 2, sliding thereon in either direction. In housing l there is a stationary central guide tube on which an additional piston l' is displaceable within the interior of the stationary piston 5. Piston l is connected to piston 3 by rod 8. Therefore pistons 2, 3 and l move always in unison.

To housing l are connected control heads 9 and le for the pressure medium of piston 2 and a control head l l for the pressure medium moved by pistons 3, 5 and l acting as pressure generators.

The drive piston 2 may be driven by fuel, steam, compressed air or other available energy. The present example relates to the employment of compressed air since this is the most frequent case.

As a medium in the pressure generator any liquid, preferably oil, may be used if, as in the present case, mostly lifting installations are concerned. Y Y

The admission of the compressed air which is either taken from a reservoir or, as needed, is supplied by an air pump, is effected through conduit l2 the admission valve I3 of which is mechanically controlled by handle I3 or automatically by a cam shaft I4. The compressed air admitted pushes piston 2 in direction I5, the air displaced by the moving piston on its rear side leaving through outlet openings in control head It.

ln the same direction as piston 2 moves piston 3 in housing Ll, the oil displaced by corresponding pressure flowing through openings i5 into the central tube S and conduit Il in control head II and through the automatic pressure valve 8 into pressure conduit i9 leading to the press of the lifting installation. Since of the pressure generating pistons 3, 5 and i, piston 3 has the largest effective cross-section, the lowest pressure stage results thereby for the initial operation of a multistage press of the lifting installation for the largest piston thereof. The oil sucked in during this motion by piston i flows from a reservoir through conduit 2l) to the automatic suction valves 2l and 22 and thereupon through conduit 23 into the annular space 24 between tube il and the inner surface of piston 5. The oil sucked in simultaneously by piston 3 iioWs through conduit 25 and suction Valves 2l and 25 and through a conduit located Within piston 5 Which conduit may take the form of a bore, channel or as shown in the illustration, may preferably be constructed as a concentrically arranged hollow space 26 with circular ring cross-section, into the interior of piston 3. At the end oi its rst stroke in direction its piston 2 automatically closes by the pickup and outlet valve 2 the air outlet openings in control head It and While simultaneously opening the supply conduit also in control head I8, guides the coinpressed air through tube 28 to the other side of piston 2 which accordingly carries out the second stroke in direction 2S. During this operation hollow piston 3 acts as a housing the oil content of which is pressed by piston 5 into pressure conduit I9 corresponding to its circular ring crosssection while pressure is created above hollow space 25 by opening the automatic pressure valve 3%. The oil quantity displaced by piston 'l iiows through conduit 23 and the pressure Valve 3l also automatically opening simultaneously into the pressure conduit, during this stroke the effective cross-sections 5 and l, which are smaller than the effective cross-section of piston 3, are added up and as a result cause by the increased oil pressure the second operating stage of the lifting press. The oil sucked in during this second stroke of piston 2 by piston 3 flows from supply conduit 2Q through the again automatic suction valves 2l and 32 and through conduit I? and pipe 6 through openings l into housing d. The opening of suction valve 32 can be effected by the aid of small piston 33 which is displaced by the increased pressure of conduit le in opposition to the action of a spring 3d and transmits this :notion by a rod structure to valve 32. During this second stroke oi piston 2 the two suction valves 2l and 22 open during the nrst stroke, and also pressure valve lil are automatically closed.

The third stroke of piston 2 which after the automatic change of the compressed air stream in control heads s and it proceeds again in direction i5, increases the pressure generated during the second stroke in conduit I9 since piston 3 during this operation presses the oil under pressure in the housing d through openings I6 and tube 6 into conduit il and the automatically opening pressure valve I8 into conduit I9. The eiective cross-section of piston 3 is then decreased by the effective cross-sections of pistons 5 and '1, is thus smaller than during the second stroke of piston 2 so that in this manner owing to the increased oil pressure the third piston stage of the lifting installation is operated. During this stroke suction valves 22, 25 and 32 are automatically opened, the latter two by small piston 3,3 which is still more displaced in opposition to the eect or spring 3Q by the increased pressure and thereby holds the two valves open by the rod structure connected thereto so that a part of the pressure oil can flow into space 2li and the interior of piston 3. Suction valve 2I during this stroke of piston 2 is closed like valves 3i! and SI..

During the fourth stroke of piston 2 in direction 29, piston l, the cross-section of which is alone effective, presses the oil through conduit 23 and the automatically opening pressure valve 3I into conduit IS while otherwise a pressure equalization takesl place through suction valves 2s and 32 subsequently opening and oil iiows from conduit 2E! through automatically opening suction Valve 2l to the extent that it is not displaced by piston 3 during this stroke through hollow space 25 and the tube 6 into housing il. Suction valve 22 and pressure Valve i3 are closed at that time. During this stroke the highest oil pressure in conduit IQ is reached and thereby the fourth stage of the lifting press is started for operation.

The interruption as well as the continuation of the operations is eiiected mechanically or automatically by handle i3 or control shaft Id respectively, which closes or opens the admission valve ci compressed air supply pipe I2. Simulta neously with the closing at the end of the :fourth stroke of piston 2 valve may be opened through lmechanical connection which valve connects the oil pressure and suction conduit is and Eil to one another so that a pressure equalization takes place and the oil is automatically forced back to the reservoir by the potential energy oi the lifting installation returning to its initial position. Valve 35 simultaneously constitutes an automatic safeguard against exceeding the maximum pressure permissible for the installation.

In an arrangement oi additional suction and pressure valves by :further combinations of the three telescoping pressure generators the number of attainable pressure stages can be increased as desired. For example, by addition or" a :further valve arrangement corresponding to the elements controlled by small piston 33, results the pos sibility of using as further steps of the eiiective cross-section piston 3 alone, the dilerence between pistons 3 and and also piston ii alone.

The `lovable pistons, piston rods and their guide elements in the described arrangement are in telescopic concentric relation which has the advantage oi an extraordinarily simple and compact construction. This is only possible by the fact that each element performs several functions.

Piston 3 constitutes simultaneously the piston rod oi' the compressed air piston 2 and the housing for piston 5 and thus has a triple function, While piston 5 also serves as housing for Piston 'i and as inner guide of piston 2, thus also serves a triple purpose.

In the particular arrangement of the elements of the pressure generator and of the performances of several tanks the described automatically acting valve arrangement in the control head H, it is made possible to render the effective cross-sections effective alone or to couple them in added or subtracted relation during successive strokes of the drive piston in a manner corresponding to the respective requirements and to thereby obtain the required necessary number of pressure steps.

As a matter of course the plant of the described kind may be employed not only for lifting installations. Fundamentally it may also be employed as high pressure lubricating press, lubricant measuring pump, conveying pressure generator, as pressure generator in metal presses, stamping, hydraulic hammers and the like, that is its employment within the meaning of the invention is possible everywhere where the generation of pressure of different valves in a steplike manner corresponding to purpose is concerned.

What we claim as new and want to secure by Letters Patent is the following:

l. A multistage pump comprising a penurnatic cylinder, a double-acting piston movable within the cylinder, a conduit connected to a source of pneumatic pressure, means connected to the cylinder and conduit and alternately directing the pneumatic pressure medium to opposite sides of the piston, a hydraulic cylinder connected to the pneumatic cylinder, a plurality of the plungers including a double-acting plunger rigid with the pneumatic piston and slidable in the hydraulic cylinder, the plurality of plungers also including plungers in slidable relation to the piston, a hydraulic reservoir, a hydraulic suction inlet conduit connected at one end to the reservoir and at the other end to the hydraulic cylinder, a hydraulic outlet conduit connected to the hydraulic cylinder, and automatic valve means increasing the pressures of the plungers in the hydraulic outlet conduit successively during successive strokes of the piston.

2. The pump according to claim 1 and wherein the first plunger constitutes the piston rod of the piston and one of the remaining plungers is stationary and of a cross-section smaller than that of the first plunger and guides the piston.

3. The pump according to claim 1 and wherein the first plunger constitutes the piston rod of the piston and comprising a central hollow rod guiding the first plunger and constituting a conduit for the hydraulic pressure medium.

4. The pump according to claim 1 and wherein the rst plunger is hollow and connected to a third plunger having a smaller cross-section than a second stationary plunger guiding the piston.

5. The pump according to claim 1 and wherein the first plunger is hollow and guided by a second stationary plunger and connected to a third plunger guided within the second plunger.

6. The pump according to claim 1 and wherein the first plunger constitutes the piston rod of the piston and comprising a central hollow rod guiding the first plunger and having one end adjacent the hydraulic cylinder top and having openings adjacent thereto and being at the other end connected to a valve housing having valves automatically establishing communication with the interior of the stationary plunger,

7. The pump according to claim 1 and wherein the iirst plunger is the piston rod of the piston guided by a second smaller and stationary hollow plunger having a hollow wall, a valve housing, the hollow of the plunger wall constituting the connection between the interior of the rst plunger and the valve housing and the interior of the second stationary plunger.

8. The pump according to claim l and wherein the rst plunger constitutes the piston rod of the piston, the piston being guided by a second, stationary, hollow plunger of smaller cross-section than that of the first plunger and having a hollow wall, a valve housing, the hollow of the wall constituting the connection between the interior of the iirst plunger and the valve housing.

9. The pump according to claim 1 and wherein the iirst plunger constitutes the piston rod of the piston and comprising a central hollow rod guiding the first plunger and having one end adjacent the hydraulic cylinder top and having openings adjacent thereto, a valve housing connected to the other end of the hollow and to the hydraulic inlet conduit, suction valves in the hydraulic outlet conduit, and a spring-loaded plunger and rod opening the suction valves.

l0. The pump according to claim 1 and wherein the first plunger constitutes the piston rod of the piston and comprising a hollow rod guiding the rst plunger and having one end adjacent the hydraulic cylinder top and having holes adjacent thereto, a valve housing connected to the other end of the hollow rod and connected to the hydraulic inlet conduit, a spring-loaded valve in the hydraulic inlet conduit and constituting safetyvalve and a valve connecting to the hydraulic inlet conduit.

11. The pump according to claim 1 and wherein the first plunger constitutes the piston rod of the piston and comprising a central hollow rod guiding the rst plunger and having one end adjacent the hydraulic cylinder top and having openings adjacent thereto, and also comprising a valve housing connected to the other end of the hollow rod, and control means in the valve housing for the pneumatic pressure medium driving the piston.

12. The pump according to claim 1 and wherein the rst plunger constitutes the piston rod of the piston and comprising a central hollow rod guiding the first plunger, and having one end near the hydraulic cylinder top and having openings adjacent thereto, and comprising a valve housing connected to the other end of the hollow rod, a hydraulic safety valve in the valve housing, a control valve for the pneumatic pressure medium connected to the hydraulic safety valve and opening upon closing the safety valve and closing upon opening the safety valve.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 262,864 Waring Aug. 15, 1882 521,432 Chaplin June 12, 1894 722,416 Stumpf Mar. 10, 1903 938,004 Leyner Oct. 26, 1909 1,008,519 Barr Nov. 14, 1911 2,205,793 Hunt June 25, 1940 

